Field of the Invention
The invention relates to apparatus used to monitor the environmental conditions inside sealed containers, and more particularly to monitor the conditions in containers such as projectiles which contain energetic materials.
Energetic materials such as explosives and propellants are particularly susceptible to change when subjected to variations in the amount of water present inside the projectile or other container. Depending upon the nature of the energetic material, an increase of water content can retard or enhance the likelihood of detonation at the time of use, and can even cause premature detonation; and a decrease of water through absorption or leakage of moisture can have similar deleterious effects on other energetic material. Some explosives and propellants self-detonate when the amount of water or water vapor is changed, so as to initiate or retard reactions that are effected by moisture.
Heretofore, efforts have been made to monitor the conditions of containers as the container is exposed to potential changes in moisture content. Other than by the very undesirable option of opening the container and physically inspecting it periodically, with the attendant costs and opportunity for moisture contamination, no effective way has yet been developed to accomplish such effective monitoring. Statistically based sampling of some of a large number of similar containers, such as stockpiled projectiles and the like, can statistically monitor a large sampling. This method is expensive, however, as destructive testing is the only reliable method presently available to evaluate the condition of the energetic material inside the container. This method, moreover, is time-limited, as well as being number limited by the quantity of samples which must be distructively used for periodic testing. Eventually, the sample becomes a major portion of the total lot size. Moreover, unexpected changes in environment will cause additional testing to be required, thus further shortening the total reliable sampling time. Proper test equipment such as a firing range may not be readily accessible to the principal storage place of the product, thus raising further inadequacies or inaccuracies due to required transportation of the samples.
Other proposals to monitor containers which are exposed to changes in conditions are also not effective in providing complete lot reliability as to the effect of such changes. For example, when temperature can be monitored externally and that data used to calculate the pressure based upon the amount of moisture originally in the container, there is no way to determine if absorption of the moisture or chemical reaction to produce additional moisture has taken place. Thus, the measurement is somewhat meaningless. Even when reliable relative humidity data is obtained from within a container, such as by calculation or measurement, changes in absolute quantities of moisture cannot be ascertained.
Accordingly, it would be of a great advantage to the art if a multiple sensor condition monitoring device could be provided for use with an enclosed container which would provide a way of determining the absolute amount of moisture within a container. It would be valuable if such a device could be provided which would permit monitoring of the conditions in the container so as to determine accurately when any change in the conditions inside the container take place which cause a change in the amount of water present in the interior.